How much does it cost to fix Alpha error code Flashing red A or B?

Typical repair cost for the Alpha Flashing red A or B fault is £100-£250 including labour.

Flashing red A or B High

Alpha Flashing red A or B Fault Code

Q: What does the Alpha Flashing red A or B fault code mean?

Your boiler has got too hot and has shut itself down as a safety precaution to prevent damage.

Also written as FLASHINGREDAORB — same fault.

The Alpha Flashing red A or B fault code means: your boiler has got too hot and has shut itself down as a safety precaution to prevent damage.. It appears on 1 Alpha model in our database.

Technical description: Overheat thermostat has operated / Temperature sensor fault

Typical repair cost £100-£250 (including labour)

DIY fix possible

Check that all radiator valves are fully openCheck that the boiler pressure is between 1.0 and 1.5 barTurn the selector switch to the 'RESET' position for a few seconds and then back to 'ON'

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Alpha models that show the Flashing red A or B fault code

Click a model for the full fault code list and model-specific repair notes.

FMK Repair: £100-£250

Source

Alpha Flashing red A or B fault code information on this page is sourced and cross-checked against the official Alpha service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026